Sheet-fed treating device

ABSTRACT

A processing unit of the invention is a single wafer processing unit including: a processing container that can be vacuumed; a stage arranged in the processing container, on which an object to be processed can be placed; a discharging pipe connected to a bottom part of the processing container and extending substantially downward linearly; a vacuum pump directly connected to the discharging pipe; and a stage-supporting pillar arranged to extend in a substantially central portion of the discharging pipe and in a direction of the discharging pipe, the stage-supporting pillar supporting the stage.

FIELD OF THE INVENTION

[0001] This invention relates to a single wafer processing unit that cancarry out a process such as an etching process, a film-forming processor an annealing process, to semiconductor wafers or the like one by one.

BACKGROUND ART

[0002] In general, in order to manufacture a desired semiconductorintegrated circuit, various processes including a film-forming process,an etching process, an oxidation-diffusion process, an annealing processor the like are carried out repeatedly to a substrate such as asemiconductor wafer. When the various processes are carried out, anecessary gas corresponding to a kind of the process, for example afilm-forming gas for a film-forming process, ozone gas for an annealingprocess or an etching gas for an etching process (including a plasmaetching process), is introduced into a processing container.

[0003] In the above case, the atmosphere in the processing container hasbeen evacuated in order to maintain a pressure suitable for the kind ofthe process. It is requested that the evacuated gas flows uniformly withrespect to the surface of the semiconductor wafer, in order to highlymaintain uniformity of the process within the surface.

[0004] Herein, a conventional general processing unit for removing anatural oxidation film (SiO₂) or the like deposited on the surface of asemiconductor wafer by using plasma (for example, Japanese-TranslatedPatent Laid-Open Publication of PCT application No. 2000-511700) isexplained. FIG. 7 is a schematic structural view of a conventionalgeneral processing unit of single-fed type. FIG. 8 is a plan view of aportion including the stage in FIG. 7.

[0005] As shown in FIG. 7, the processing unit using plasma has aprocessing container 2, for example having a cylindrical shape and madeof aluminum. In the processing container 2, a stage 6 is arranged on atip end of a hollow and wide supporting arm 4 that extends from a sidewall of the container. A semiconductor wafer W is adapted to be placedon the stage 6. A large numbers of gas holes 7 that introduce a processgas, such as a plasma gas including Ar gas, H₂ gas and so on, into theprocessing container 2 are arranged at an upper portion of the sidewallof the processing container 2 in a circumferential direction thereof.

[0006] A ceiling part of the processing container 2 is open. A ceilingdome 8 having a cylindrical shape and a closed ceiling is hermeticallyarranged on the ceiling part. The ceiling dome 8 is made of for examplequartz. An inductive coupling coil 10 is wound on an outside wall of theceiling dome 8. A high-frequency wave of for example 450 kHz is adaptedto be applied from a high-frequency electric power source 12 forinductively coupled plasma to the inductive coupling coil 10.

[0007] The stage 6 is made of for example ceramics such as aluminumnitride (AlN). A resistance heater 14 and a bias electrode 16 are buried(incorporated) in the stage 6. The resistance heater 14 is connected toan electric power source for heater. The bias electrode 16 is connectedto a high-frequency electric power source 16 for biasing, whichgenerates a high-frequency wave of for example 13.56 MHz.

[0008] A discharging pipe 18 with a large aperture is connected to acentral portion of a bottom part of the processing container 2. Thedischarging pipe 18 extends downward and linearly by a predeterminedlength. A flow-way adjusting valve 20 and a vacuum pump 22 are providedin that order in the discharging pipe 18 in order to evacuate theprocessing container 2. The vacuum pump 22 consists of for example aturbo molecular pump. In addition, a flange at an outlet port of thevacuum pump 22 is connected to a discharging duct 24. Thus, thedischarged gas is adapted to flow into a final gas abatement system (notshown).

SUMMARY OF THE INVENTION

[0009] In the above conventional unit, the process gas (plasma gas) issupplied substantially uniformly from the large number of gas holes 7provided at the upper portion of the side wall of the processingcontainer 2 into a processing space S in the processing container 2.Then, the process gas is made plasma by inductively coupling. Theplasmatic gas (that has been made plasma) flows downward while etchingthe surface of the wafer, passes around the stage 6 and flows into thedischarging pipe 18 (to be evacuated).

[0010] However, in the unit, the wide supporting arm 4 for supportingthe stage 6 is mounted at the side wall of the processing container.Thus, the supporting arm 4 blocks and/or partializes the evacuated flowof the atmosphere in the processing container 2. That is, the flow ofthe discharged gas (the atmosphere in the processing container) is notuniform on and above the surface of the wafer. Therefore, thepredetermined process, herein the etching process, is also not uniformwithin the wafer surface, so that the uniformity within the surface isdeteriorated.

[0011] This invention is intended to solve the above problems. Theobject of this invention is to provide a single wafer processing unitwhich can improve uniformity within a surface of an object to beprocessed placed on a stage during various processes by substantiallyuniformly evacuating the atmosphere in a processing space through aroundthe stage.

[0012] This invention is a single wafer processing unit comprising: aprocessing container that can be vacuumed; a stage arranged in theprocessing container, on which an object to be processed can be placed;a discharging pipe connected to a bottom part of the processingcontainer and extending substantially downward linearly; a vacuum pumpdirectly connected to the discharging pipe; and a stage-supportingpillar arranged to extend in a substantially central portion of thedischarging pipe and in a direction of the discharging pipe, thestage-supporting pillar supporting the stage.

[0013] According to the present invention, the atmosphere in theprocessing container can be substantially uniformly evacuated anddischarged through around the stage, without partialized. Thus, the gasflow on and above a surface of the object to be processed can be madeuniform within the surface. Therefore, the uniformity of a processwithin the surface can be improved.

[0014] Preferably, the stage-supporting pillar is attached to thedischarging pipe by means of an attachment plate that extends in thedirection of the discharging pipe.

[0015] The attachment plate may be formed by a plate member thin enoughthat the plate member doesn't block the flow of discharged gas.

[0016] Preferably, a plurality of attachment plates is arrangedspokewise around and from the stage-supporting pillar.

[0017] In addition, the stage-supporting pillar may have a hollow pipemember that extends in the direction of the discharging pipe.

[0018] An electric-power supplying line may be arranged in the hollowpipe member.

[0019] A lower part of the hollow pipe member may be connected to aline-taking-off pipe that extends through a side wall of the dischargingpipe.

[0020] Preferably, the stage-supporting pillar may be attached to thedischarging pipe by means of the line-taking-off pipe. In the case, morepreferably, the stage-supporting pillar is also attached to thedischarging pipe by means of an attachment plate that extends in thedirection of the discharging pipe. Further preferably, at least a partof the discharging pipe, at least a part of the hollow pipe member, theattachment plate and the line-taking-off pipe are integratedly formed.

[0021] In addition, for example, the discharging pipe has a circularsection, and the line-taking-off pipe extends in a diametral directionof the discharging pipe, through two diametrally-opposite portions of aside wall of the discharging pipe, from a lower part of the hollow pipemember.

[0022] Alternatively, the discharging pipe has a circular section, andthe line-taking-off pipe extends in a radial direction of thedischarging pipe, through one portion of a side wall of the dischargingpipe, from a lower part of the hollow pipe member.

[0023] Alternatively, the line-taking-off pipe extends through twoportions of a side wall of the discharging pipe, from a lower part ofthe hollow pipe member, and the electric-power supplying line isseparated into a first line that extends through one portion of the sidewall and a second line that extends through the other portion of theside wall.

[0024] In the case, for example, the first line is an electric-powersupplying line through which a high-frequency electric current flows,and the second line is an electric-power supplying line through which nohigh-frequency electric current flows.

[0025] Preferably, a coolant circulating way may be formed in parallelwith the first and second lines.

[0026] In addition, preferably, a flow-way adjusting valve that controlsa flow-way area of the discharging pipe is arranged on an upstream sideof the vacuum pump.

[0027] In addition, preferably, a high-frequency coil connected to ahigh-frequency electric power source for inductively coupled plasma isarranged at a ceiling part of the processing container, and a biaselectrode connected to a high-frequency electric power source forbiasing is provided in the stage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a structural view showing an embodiment of a singlewafer processing unit according to the present invention;

[0029]FIG. 2 is a sectional view taken along A-A line of FIG. 1;

[0030]FIG. 3 is a sectional view taken along B-B line of FIG. 1;

[0031]FIG. 4 is a partial sectional view showing a part of anotherembodiment of a processing unit according to the present invention;

[0032]FIG. 5 is a sectional view taken along C-C line of FIG. 4;

[0033]FIG. 6 is a structural view showing another embodiment of aprocessing unit according to the present invention;

[0034]FIG. 7 is a schematic structural view showing a conventionalgeneral single wafer processing unit; and

[0035]FIG. 8 is a plan view showing a portion including the stage inFIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0036] Hereinafter, an embodiment of a single wafer processing unitaccording to the present invention is explained with reference toattached drawings.

[0037]FIG. 1 is a structural view showing the embodiment of a singlewafer processing unit of the present invention. FIG. 2 is a sectionalview taken along A-A line of FIG. 1. FIG. 3 is a sectional view takenalong B-B line of FIG. 1.

[0038] The processing unit of the embodiment is formed as a processingunit for etching a natural oxidation film by using inductively coupledplasma (ICP).

[0039] As shown in FIGS. 1 to 3, the processing unit 26 has a processingcontainer 28 made of aluminum, which has for example a cylindrical shapeand an open ceiling part. A disk-like stage 30, on which a semiconductorwafer W as an object to be processed is placed, is arranged at a centralportion of the processing container 28. The stage 30 is made of forexample ceramics such as aluminum nitride (AlN). If necessary, aresistance heater 32 as heating means and/or a bias electrode 34 forapplying a high-frequency voltage has been previously buried in thestage 30.

[0040] A plurality of, for example three, pin holes 36 are formedvertically through the stage 30 (only two are shown in FIG. 1). Alifting pin 40 is freely contained in each pin hole 36. A linking ring38 commonly links respective lower ends of the lifting pins 40. Thelifting pin 40 is made of for example ceramics. The linking ring 38 issupported and can be vertically moved by a lifting rod 42, whichpenetrates a bottom part of the processing unit 28 and can be verticallymoved. If the linking ring 38 i.e. the lifting pins 40 are verticallymoved, the wafer W can be also lifted up and down.

[0041] A bellows 44 made of metal is arranged at a portion penetrated bythe lifting rod 42 in the bottom part of the processing container. Thus,airtightness in the processing container 28 can be maintained while thelifting rod 42 can be vertically moved.

[0042] In addition, above a peripheral portion of the stage 30, a shadowring for protecting a peripheral portion of the wafer and a peripheralportion of the stage from an etching process during the etching processcan be provided in such a manner that it can be vertically moved, butnot shown.

[0043] A ceiling dome 46 that has a short cylindrical shape and a closedceiling end is hermetically arranged on the open ceiling part of theprocessing container 28 via a sealing member 48 such as an O-ring. Theceiling dome 46 is made of for example quartz. A high-frequency coil 50for inductively coupled plasma is wound around the ceiling dome 46 byten and several turns. The high-frequency coil 50 is connected to ahigh-frequency electric power source 54 for inductively coupled plasmaof for example 450 kHz via a matching circuit 52.

[0044] A gate valve 56, which can be opened and closed when the wafer Wis loaded or unloaded, is provided at an upper portion of a side wall ofthe processing container 28. A large number of, for example twenty,gas-ejecting holes 58 are formed at another upper portion of the sidewall of the processing container 28 in a circumferential directionthereof as gas-supplying means. A process gas such as a plasma gas,whose flow rate has been controlled, can be supplied into the processingcontainer 28 through the gas-ejecting holes 58.

[0045] An opening 62 with a large aperture, whose diameter is about 210mm, is formed at a substantially central portion of the bottom part 60of the processing container 28, while the inside diameter of theprocessing container 28 is about 362 mm. A discharging pipe 64 with asimilar large aperture is hermetically connected to the opening 62 via asealing member 66 such as an O-ring so that it extends downward(vertically) and substantially linearly. Thus, thedischarging-conductance is as large as possible.

[0046] More concretely, the discharging pipe 64 mainly consists of: anupper pipe 64A connected to the bottom part 60, a lower pipe 64C whosediameter is small, and a pipe-diameter adjusting pipe 64B whose diameteris gradually reduced to adjust a pipe diameter thereof from a lower endof the upper pipe 64A to an upper end of the lower pipe 64C. Sealingmembers 65, 68 such as O-rings are provided at connecting portionsbetween the respective pipes 64A to 64C to maintain aritightnesstherebetween. A vacuum pump 98 is connected to a lower end of the lowerpipe 64C. Another discharging pipe 72 is connected to a gas-dischargingflange 99 provided at a side portion of the vacuum pump 98, via asealing member 70 such as an O-ring.

[0047] A stage-supporting pillar 74 for supporting the stage 30 isarranged in a substantially central portion in the upper pipe 64A of thedischarging pipe 64 coaxially therewith. The stage-supporting pillar 74is made of for example aluminum. More concretely, the stage-supportingpillar 74 consists of an upper hollow pipe member 74A and a lower hollowpipe member 74B that is hermetically connected to a lower end portion ofthe upper hollow pipe member 74A via a sealing member 76 such as anO-ring. An upper end of the upper hollow pipe member 74A is hermeticallyconnected to a lower surface of the stage 30 and is adapted to supportthe stage 30.

[0048] The lower hollow pipe member 74B and the upper pipe 64A form akind of double-tube structure. The discharged gas is adapted to flowthrough a doughnut space 77 (see FIG. 2) between their members. Aplurality of, four in the shown example, spokewise attachment plates 78(see FIG. 2) are arranged at substantially the same interval in acircumferential direction in order to connect an outside wall of thelower hollow pipe member 74B and an inside wall of the upper pipe 64A.The attachment plates 78 are adapted to bear loads of the stage 30 andthe stage-supporting pillar 74. In addition, in the case, the space 77is divided into four partial spaces by the attachment plates 78.

[0049] In addition, the attachment plates 78 are provided along a flowdirection of the discharged gas i.e. along a vertical direction. Thus,the gas-discharging (exhausting) resistance can be reduced as much aspossible. The number of attachment plates 78 is not limited to four. Thenumber of attachment plate 78 may be reduced to two or three in order toreduce the gas-discharging resistance more.

[0050] A hollow line-taking-off pipe 80, which laterally penetrates theupper pipe 64A and crosses the space 77 orthogonally to the gas flow, isconnected to the lower end of the lower hollow pipe member 74B of thestage-supporting pillar 74 in such a manner that they communicate witheach other. The line-taking-off pipe 80 is also adapted to bear theloads of the stage 30 and the stage-supporting pillar 74. The lower endsof the attachment plates 78 are connected to upper-end portions of anoutside wall of the line-taking-off pipe 80. If the strength of theline-taking-off pipe 80 is set to be high enough to bear the loads, itis possible to omit attaching the attachment plates 78.

[0051] A sealing member 82 such as an O-ring is provided at a portion ofthe upper pipe 64A penetrated by the line-taking-off pipe 80. Thus,airtightness in the discharging pipe 64 can be maintained. On the otherhand, the inside of the line-taking-off pipe 80 and the inside of thestage-supporting pillar 74 communicate with outside atmosphere to beunder the atmospheric pressure. A heater cable 84 that is connected tothe resistance heater 32 and a high-frequency cable 86 that is connectedto the bias electrode 34 are inserted in the line-taking-off pipe 80, aselectric power supplying lines. The other end of the heater cable 84 isconnected to an electric power source for heater (not shown). The otherend of the high-frequency cable 86 is connected to a high-frequencyelectric power source 90 for biasing that outputs a high frequencyvoltage for biasing of for example 13.56 MHz, via a matching circuit 88.

[0052] A cooling jacket 92 is provided at a connecting portion betweenthe upper hollow pipe member 74A and the lower hollow pipe member 74B ofthe stage-supporting pillar 74, in order to prevent thermal damage ofthe sealing member 76 provided at the portion. A coolant circulating way94 for causing a coolant to flow into the cooling jacket 92 is insertedin the stage-supporting pillar 74 and in the line-taking-off pipe 80.

[0053] A flow-way adjusting valve 96 consisting of a three-position gatevalve is provided in the lower pipe 64C of the discharging pipe 64. Theflow-way adjusting valve 96 can adjust a flow-way area at three stagesfrom a full-open state of the discharging pipe 64 to a full-closed statethereof. A throttle valve or the like, which can continuously adjust theflow-way area, can be used as the flow-way adjusting valve 96 instead ofthe above gate valve.

[0054] A vacuum pump 98 consisting of for example a turbo-molecular pumpor the like is directly connected to the lower pipe 64C just below theflow-way adjusting valve 96. In the case, an inlet port 98A of thevacuum pump 98 is arranged orthogonally to the flow of the dischargedgas. Thus, the gas-discharging resistance is reduced as much aspossible.

[0055] The length H1 of the upper hollow pipe member 74A is set to befor example about 159 mm, in order to obtain temperature gradient enoughthat the sealing member 76 under a cooled state thereof is not thermallydeteriorated.

[0056] Herein, in the above embodiment, the upper pipe 64A, thepipe-diameter adjusting pipe 64B, the attachment plates 78, theline-taking-off pipe 80 and the lower hollow pipe member 74B arerespectively provided as separate members. However, these members may beformed integratedly, for example by cutting out an aluminum block.According to the latter, it is possible to enhance credibility ofsealing characteristic and mechanical strength.

[0057] Next, an operation of the above embodiment is explained.

[0058] At first, an unprocessed semiconductor wafer W held by aconveying arm not shown is loaded into the processing container 28through the opened gate valve 56. The wafer is transferred onto thelifting pins 40. Then, the lifting pins 40 are moved downward, so thatthe wafer W is placed onto the stage 30.

[0059] The stage 30 has been previously heated to a predeterminedtemperature, preliminary. After the wafer W is placed on the stage 30,electric power supplied to the resistance heater 32 is increased, sothat the wafer W is heated to a predetermined process temperature, forexample 600° C., and the process temperature is maintained.

[0060] Then, the process gas whose flow rate has been controlled, suchas Ar gas and/or H₂ gas as a plasma gas, is supplied into the processingcontainer 28 from the respective gas-ejecting holes 58 provided at theupper portion of the side wall of the processing container 28. At thesame time, the processing container 28 is vacuumed by the vacuum pump98, so that the inside of the processing container 28 is maintained at apredetermined pressure, for example of about 5 mTorr (0.7 pa) to 5 Torr(665 pa). In addition, at the same time, the high-frequency electricpower for biasing of 13.56 MHz is applied to the bias electrode 34buried in the stage 30. On the other hand, the high-frequency electricpower of 450 kHz is applied to the high-frequency coil 50 wound aroundthe ceiling dome 46. Thus, inductive coupling is generated, and plasmais generated in the processing space S. That is, activated species ofargon gas and/or hydrogen are generated, and a natural oxidation film orthe like on the surface of the wafer on the stage 30 is etched.

[0061] In the embodiment, the process gas introduced from the respectivegas-ejecting holes 58 into the processing container 28 is made plasma,and hence becomes activated species, and is evacuated to flow outside ofthe stage 30 and vertically through the discharging pipe 64. Herein,differently from the conventional unit shown in FIG. 7, the stage 30 issupported by the stage-supporting pillar 74 that extends in the verticaldirection and coaxially in the discharging pipe 64. Thus, substantially,there is no member that blocks the flow of the discharged gas in theprocessing container 28. Therefore, the discharged gas can be evacuatedsubstantially uniformly around the stage 30 without partialized. As aresult, the gas flow on and above the wafer surface can be made uniform,plasma density can be also made uniform within the surface, and henceuniformity of the plasma process within the surface can be remarkablyenhanced.

[0062] In addition, the attachment plates 78 that fix thestage-supporting pillar 74 to the discharging pipe 64 are very thin, andmoreover they are arranged along the direction of the discharged gasflow. Thus, they hardly become any gas-discharging resistance. That is,high gas-discharging conductance can be maintained. The attachmentplates 78 are made of for example aluminum.

[0063] In addition, similarly, since the vacuum pump 98 is directlyattached to the lower pipe 64C of the discharging pipe 64 that extendsin a substantially vertical direction and linearly from the bottom partof the processing container 28, the atmospheric gas in the processingcontainer 28 can be smoothly evacuated. Thus, higher gas-dischargingconductance can be maintained.

[0064] The position where the line-take-off pipe 80 crossing the insideof the discharging pipe 64 is attached is located much lower than thebottom part 60 of the processing container 28. Thus, it is seldom thatthe line-take-off pipe 80 disturbs the flow of the atmospheric gas inthe processing container 28 and/or becomes a large gas-dischargingresistance.

[0065] In addition, the length of the stage-supporting pillar 74supporting the stage 30 is set to be enough long, and thus thetemperature gradient of the stage-supporting pillar 74 is small enoughthat the temperature gradient doesn't badly affect temperaturedistribution of the stage 30. Thus, temperature distribution of thewafer is not affected badly.

[0066] In the above embodiment, the line-take-off pipe 80 for taking offthe electric power supplying lines such as the heater cable 84 and thehigh-frequency cable 86 is provided to diametrally cross the section ofthe upper pipe 64A that is a flow way. However, this invention is notlimited to that manner. The line-take-off pipe 80 may be provided onlyat a radial portion of the upper pipe 64A.

[0067]FIG. 4 is a partial sectional view showing a part of an embodimentof such a unit according to the present invention. FIG. 5 is a sectionalview taken along C-C line of FIG. 4. In the embodiment, other portionsnot shown in FIG. 4 are the same as the structure shown in FIG. 1. Asshown in FIGS. 4 and 5, in the embodiment, the line-taking-off pipe 80Ais connected to the lower end of the lower hollow pipe member 74B of thestage-supporting pillar 74 and extends in a radial direction thereof topenetrate one portion of the side wall of the discharging pipe 64. Thus,the stage-supporting pillar 74 is cantilevered.

[0068] Compared with the structure of the line-take-off pipe 80 shown inFIG. 1, in the case of the line-take-off pipe 80A shown in FIGS. 4 and5, the gas-discharging resistance is smaller by that an attachment ofanother line-take-off pipe in a radial direction opposite to theline-take-off pipe 80A is omitted, that is, the discharged gas can beevacuated more smoothly.

[0069] Of course, if the discharging pipe 64 has two penetratedportions, like the case of the line-take-off pipe 80 shown in FIG. 1,for example, a high-frequency electric power system (high-frequencycable 86) and the other electric power systems (heater cable 84) may beseparately formed. The coolant circulating way 94 may be formed for eachelectric power system.

[0070] In the above embodiments, the etching unit by means ofinductively coupled plasma is explained. However, this invention is notlimited thereto. This invention is applicable to any other type ofetching unit. For example, this invention is applicable to aparallel-plate type of processing unit or the like.

[0071] Furthermore, this invention is not limited to the etching unit,but also applicable to a CVD film-forming unit, an oxidation-diffusionunit, an ashing unit, a modification unit, or the like. In addition, theheating means is not limited to the resistance heater, but could be aheating lamp.

[0072] For example, FIG. 6 is a schematic structural view of aprocessing unit for a thermal CVD film-forming process as anotherembodiment of a processing unit according to the present invention. Thesame parts as shown in FIG. 1 are designated by the same numeral signs,and explanation thereof is omitted.

[0073] In the embodiment, a showerhead 102 having a lot of gas-ejectingholes 100 as gas-supplying means is arranged at the ceiling part of theprocessing container 28, instead of the ceiling dome 46 and thehigh-frequency coil 50. Thus, a thermal CVD process can be carried out.Thus, in the embodiment, the gas-ejecting holes 58, the bias electrode34, the high-frequency electric power source for biasing 90 and so on,shown in FIG. 1, are omitted.

[0074] According to the embodiment, the gas flow on and above the wafersurface can be made uniform without partialized. Thus, the process canbe carried out more uniformly, that is, uniformity of film-thicknesswithin the surface can be enhanced.

[0075] In addition, in the above embodiments, the semiconductor wafer isexplained as an object to be processed. However, this invention is notlimited thereto, but also applicable to a LCD substrate, a glasssubstrate and so on.

1. A single wafer processing unit comprising: a processing containerthat can be vacuumed, a stage arranged in the processing container, onwhich an object to be processed can be placed, a discharging pipeconnected to a bottom part of the processing container and extendingsubstantially downward linearly, a vacuum pump directly connected to thedischarging pipe, and a stage-supporting pillar arranged to extend in asubstantially central portion of the discharging pipe and in a directionof the discharging pipe, the stage-supporting pillar supporting thestage.
 2. A single wafer processing unit according to claim 1, whereinthe stage-supporting pillar is attached to the discharging pipe by meansof an attachment plate that extends in the direction of the dischargingpipe.
 3. A single wafer processing unit according to claim 2, whereinthe attachment plate is formed by a plate member thin enough that theplate member doesn't block the flow of discharged gas.
 4. A single waferprocessing unit according to claim 2 or 3, wherein a plurality ofattachment plates is arranged spokewise around and from thestage-supporting pillar.
 5. A single wafer processing unit according toany of claims 1 to 4, wherein the stage-supporting pillar has a hollowpipe member that extends in the direction of the discharging pipe.
 6. Asingle wafer processing unit according to claim 5, wherein anelectric-power supplying line is arranged in the hollow pipe member. 7.A single wafer processing unit according to claim 5 or 6, wherein alower part of the hollow pipe member is connected to a line-taking-offpipe that extends through a side wall of the discharging pipe.
 8. Asingle wafer processing unit according to claim 7,wherein thestage-supporting pillar is attached to the discharging pipe by means ofthe line-taking-off pipe.
 9. A single wafer processing unit according toclaim 8, wherein the stage-supporting pillar is also attached to thedischarging pipe by means of an attachment plate that extends in thedirection of the discharging pipe, and at least a part of thedischarging pipe, at least a part of the hollow pipe member, theattachment plate and the line-taking-off pipe are integratedly formed.10. A single wafer processing unit according to any of claims 7 to 9,wherein the discharging pipe has a circular section, and theline-taking-off pipe extends in a diametral direction of the dischargingpipe, through two diametrally-opposite portions of a side wall of thedischarging pipe, from a lower part of the hollow pipe member.
 11. Asingle wafer processing unit according to any of claims 7 to 9, whereinthe discharging pipe has a circular section, and the line-taking-offpipe extends in a radial direction of the discharging pipe, through oneportion of a side wall of the discharging pipe, from a lower part of thehollow pipe member.
 12. A single wafer processing unit according to anyof claims 7 to 9, wherein the line-taking-off pipe extends through twoportions of a side wall of the discharging pipe, from a lower part ofthe hollow pipe member, and the electric-power supplying line isseparated into a first line that extends through one portion of the sidewall and a second line that extends through the other portion of theside wall.
 13. A single wafer processing unit according to claim 12,wherein the first line is an electric-power supplying line through whicha high-frequency electric current flows, and the second line is anelectric-power supplying line through which no high-frequency electriccurrent flows.
 14. A single wafer processing unit according to claim 12or 13, wherein a coolant circulating way is formed in parallel with thefirst and second lines.
 15. A single wafer processing unit according toany of claims 1 to 14, wherein a flow-way adjusting valve that controlsa flow-way area of the discharging pipe is arranged on an upstream sideof the vacuum pump.
 16. A single wafer processing unit according to anyof claims 1 to 15, wherein a high-frequency coil connected to ahigh-frequency electric power source for inductively coupled plasma isarranged at a ceiling part of the processing container, and a biaselectrode connected to a high-frequency electric power source forbiasing is provided in the stage.